During mammalian embryogenesis, the first differentiation event that occurs leads to a polarization of the outer cells of the 16-cell morula. This outer layer of cells forms the trophectoderm and the inner, apolar clump of cells become the inner cell mass. The inner cell mass will give rise to:

the entire embryo

Explanation:

The trophectoderm refers to the polarized single cell layer that forms the wall of the blastocyst, thereby forming the first epithelium during embryogenesis. Moreover, the blastocyst is composed of 1-an inner cell mass (ICM) which will form all the tissues of the embryo's body, and 2-an outer layer composed of cells collectively called the trophoblast. The ICM of the blastocyst will form the embryoblast (which subsequently will give rise to the embryo itself) and the fetus, while the trophoblast will form all of the supporting tissues (i.e., amniotic sac, placenta, and umbilical cord). In humans, the blastocyst is the developmental stage of the embryo on day 5 after fertilization.

an individual’s sex (i.e., whether they are a male or female) is determined by the sex chromosomes. most people have two sex chromosomes, one that is inherited from their mother and one that is inherited from their father. typically, females have two x chromosomes (xx) and males have one x chromosome and one y chromosome (xy). conditions caused by changes (“mutations”) in genes located on the x chromosome are considered x-linked.

x-linked recessive inheritance

most x-linked conditions are recessive. this means that in a person with two x chromosomes (most females), both copies of a gene (i.e., one on each x chromosome) must have a change or mutation whereas in a person with one x chromosome (most males), only one copy of a gene must have a mutation. a female with a mutation in one copy of a gene on the x chromosome is said to be a “carrier” for an x-linked condition. a male with a mutation in a gene on the x chromosome is typically affected with the condition. because females have two copies of the x chromosome and males have only one x chromosome, x-linked recessive diseases are more common among males than females. however, x-linked recessive diseases can occur in both males and females.

for x-linked recessive disorders, an unaffected carrier mother who has a mutation in a gene on the x chromosome can transmit either the x chromosome with this mutation or a “normal” x chromosome to her children. if the father is unaffected, none of her daughters will be affected and all of her daughters will be unaffected—since they will inherit at least one normal x chromosome from their father. however, each daughter will have a 50% chance of being an unaffected carrier like her mother and a 50% chance of both x chromosomes being normal.